The Peschanka/Stalingrad "bone fields" are discussed in this thread on Dan Carlin's forum. Dan cites:
- Donovan Webster, Aftermath: The Remnants of War: From Landmines to Chemical Warfare — The Devastating Effects of Modern Combat
The other main source, whom I think Dan mentions in that show, is Walter Seledec, an Austrian TV editor/official (and apparently brigadier1) who brought footage of the remains at Volgograd back to Austria.
He was interviewed for a 1993 New Yorker article2 on the complicated legacy of Stalingrad and efforts to reinter the Austrian and German war dead. When the author visited Peschanka (a village to the west of Volgograd) in January of 1993 he only saw steppes covered in snow, but he wrote that he saw Seledec's photos and quoted Seledec's Russian guide (who helped German and Austrian organisations find and identify the dead) describing his childhood playing amongst skeletons and war wreckage, and how children are still injured or killed by unexploded ordnance.
Hundreds of thousands of men on both sides were unburied, buried in mass graves—and on the German side, buried in shallow icy graves by starving frostbitten men. According to the article, shallow graves were exposed by erosion and winter thaw or by farmers' tractors, and looted for militaria.
Some cemeteries marked on military maps from the period have been dug up, but reinterment and memorialisation are contentious issues. The article quotes Seledec saying that until 1992, Russia considered the Stalingrad battlefields a "sensitive area" and were "difficult" for foreigners to access. The Austrian government was able to push for the reinterment of their war dead because they were "identified by the Allies as 'the first victim' of National Socialist aggression" (author's words, not Seledec's), whereas Germany garnered less sympathy and the understandably bitter opposition of Red Army veterans.
I haven't tried to track down Seledec's documentary, but this paragraph mentions articles which could be looked up for more information:
Seledec's revelations caused a sensation in the Austrian press. Across the country, newspapers ran front-page stories bolstered by images of the scattered skeletons. The daily Kurier published a full-page story with the headline "THE DEATH FIELDS OF STALINGRAD." In the central province of Steiermark, a local paper headlined its report "BONE-LITTERED BATTLEFIELDS." Another daily paper, under the headline "BONES WITH IDENTITY TAGS," reported, "Skulls lie in helmets, decayed bones still stand in boots, on the spines hang the identity tags." Wiener, a popular monthly magazine, featured a story accompanied by a full-page color photograph of a skeleton lying in an open field, its arms at its sides. …
Seledec has been accused of crossing the line between commemorating ordinary Wehrmacht soldiers and celebrating Nazis.3
- "German WWII soldiers get proper burial after 60 years", The Age (2008)4
- The German War Graves Commission's (Volksbund Deutsche Kriegsgräberfürsorge) page on the Rossoshka cemeteries (Russian and German), inaugurated in 19995
- Volgograd tourist website on the Rossoshka cemeteries and various tours to excavation sites and the sites of reburial ceremonies for Soviet solders6
I don't have enough rep to include more than two links in my answer, so I've put the superscripted citations here.